1. Field of the Invention
The present invention relates to a method of manufacturing hexagonal ferrite powder.
The present invention further relates to hexagonal ferrite powder that is manufactured by the above manufacturing method, and to a magnetic recording medium containing the above hexagonal ferrite powder in a magnetic layer.
2. Discussion of the Background
Hexagonal ferrite is widely employed as magnetic powder for magnetic recording. The coercive force thereof is great enough for use in permanent magnetic materials. The magnetic anisotropy that is the basis of the coercive force derives from its crystal structure. Thus, high coercive force can be maintained even when the size of the particles is reduced. Further, magnetic recording media employing hexagonal ferrite in a magnetic layer have high density characteristics due to the vertical component. Thus, hexagonal ferrite is ferromagnetic powder that is suited to high density recording.
Various methods of manufacturing hexagonal ferrite have been proposed, including the coprecipitation method, the hydrothermal synthesis method, and the glass crystallization method. Of these, manufacturing methods utilizing a continuous hydrothermal synthesis reaction (a continuous hydrothermal synthesis process) in a high-temperature, high-pressure water-based fluid have been garnering attention in recent years as methods permitting the manufacturing of hexagonal ferrite with high productivity (for example, see Japanese Unexamined Patent Publication (KOKAI) Heisei No. 6-302421 or English language family member U.S. Pat. No. 5,433,878, Japanese Unexamined Patent Publication (KOKAI) Heisei No. 8-40723, and Japanese Unexamined Patent Publication (KOKAI) No. 2009-208969, which are expressly incorporated herein by reference in their entirety).